This study investigates the atomic mechanisms of resistive switching (RS) in two-dimensional (2D) material-based memristors, focusing on MoS₂ and h-BN devices with electrochemically active and passive electrodes. Using reactive molecular dynamics (MD) simulations with a charge equilibration approach, the research reveals that RS in active electrode-based multilayer devices involves the formation and disruption of metal filaments through grain boundaries, while passive electrode-based devices require interlayer B-N bond formation and S atom popping at point defects. The study also shows that metal atom adsorption at point defects causes RS in monolayer MoS₂. The atomic-level understanding provides explanations for contradictory experimental findings and enables defect-engineering guidelines for 2D materials. The research highlights that in h-BN, electric fields induce intrinsic changes, such as the formation of interlayer N-B bridges, which lead to nonvolatile RS. The threshold electric field for forming these bridges depends on the type of defect. In multilayer h-BN, metal ions migrate through grain boundaries, forming conductive filaments that short-circuit the electrodes. The RESET process involves Joule heating, which disrupts the filament and resets the device. The study also shows that the coexistence of volatile and nonvolatile RS in some devices arises from atomic configurations at grain boundaries. In MoS₂, metal atoms adsorb at S vacancies, creating conductive paths and switching the device to LRS. The RESET process involves high local temperatures, causing metal ions to return to the electrodes and breaking the filament. The study demonstrates that the number of metal atoms in the filament affects the resistance states, with multiple resistance states arising from partial filament dissolution during RESET. The research also develops a reactive force field (ReaxFF) for Au-Mo interactions, enabling MD simulations of Au-MoS₂-Au devices. The study shows that Au adsorption at S vacancies leads to conductive paths and switching. The transport properties of the Au-MoS₂-Au system are evaluated using DFT-NEGF, revealing that conductance increases with the number of Au atoms in the grain boundary, but the increase is not linear. Overall, the study provides a detailed atomic-level understanding of RS mechanisms in 2D material-based memristors, highlighting the roles of intrinsic and extrinsic factors, and offering insights into the design and optimization of these devices for nonvolatile memory applications.This study investigates the atomic mechanisms of resistive switching (RS) in two-dimensional (2D) material-based memristors, focusing on MoS₂ and h-BN devices with electrochemically active and passive electrodes. Using reactive molecular dynamics (MD) simulations with a charge equilibration approach, the research reveals that RS in active electrode-based multilayer devices involves the formation and disruption of metal filaments through grain boundaries, while passive electrode-based devices require interlayer B-N bond formation and S atom popping at point defects. The study also shows that metal atom adsorption at point defects causes RS in monolayer MoS₂. The atomic-level understanding provides explanations for contradictory experimental findings and enables defect-engineering guidelines for 2D materials. The research highlights that in h-BN, electric fields induce intrinsic changes, such as the formation of interlayer N-B bridges, which lead to nonvolatile RS. The threshold electric field for forming these bridges depends on the type of defect. In multilayer h-BN, metal ions migrate through grain boundaries, forming conductive filaments that short-circuit the electrodes. The RESET process involves Joule heating, which disrupts the filament and resets the device. The study also shows that the coexistence of volatile and nonvolatile RS in some devices arises from atomic configurations at grain boundaries. In MoS₂, metal atoms adsorb at S vacancies, creating conductive paths and switching the device to LRS. The RESET process involves high local temperatures, causing metal ions to return to the electrodes and breaking the filament. The study demonstrates that the number of metal atoms in the filament affects the resistance states, with multiple resistance states arising from partial filament dissolution during RESET. The research also develops a reactive force field (ReaxFF) for Au-Mo interactions, enabling MD simulations of Au-MoS₂-Au devices. The study shows that Au adsorption at S vacancies leads to conductive paths and switching. The transport properties of the Au-MoS₂-Au system are evaluated using DFT-NEGF, revealing that conductance increases with the number of Au atoms in the grain boundary, but the increase is not linear. Overall, the study provides a detailed atomic-level understanding of RS mechanisms in 2D material-based memristors, highlighting the roles of intrinsic and extrinsic factors, and offering insights into the design and optimization of these devices for nonvolatile memory applications.